Drug interactions involving cimetidine--mechanisms, documentation, implications.

Area of Science:

• Pharmacology
• Drug Interactions
• Clinical Pharmacy

Background:

• Cimetidine is widely used and inhibits liver microsomal activity, potentially affecting drug metabolism and hepatic blood flow.
• Its effects on gastric secretion and intrinsic toxicity contribute to its complex pharmacological profile.
• Numerous drug interactions with cimetidine have been reported, but many require further elucidation.

Purpose of the Study:

• To review and summarize the known and potential adverse drug interactions associated with cimetidine.
• To highlight the clinical significance of these interactions for healthcare providers.
• To emphasize the need for vigilant patient monitoring during combination therapy involving cimetidine.

Main Methods:

• Literature review of reported cimetidine drug interactions.
• Categorization of interactions based on mechanism (absorption, metabolism, excretion) and clinical significance.
• Synthesis of data to provide a comprehensive overview for clinicians.

Main Results:

• Significant absorption alterations noted with ketoconazole, iron, vitamin B12, and pancreatic enzymes.
• Metabolic inhibition or decreased excretion observed with warfarin, propranolol, theophylline, phenytoin, quinidine, and certain benzodiazepines.
• Potential interactions with other agents including analgesics, caffeine, ethanol, and more, alongside effects on antacid absorption and acetaminophen toxicity.

Conclusions:

• Cimetidine exhibits complex effects on drug absorption, elimination, and toxicity, necessitating careful consideration in polypharmacy.
• Clinicians must remain alert to both increased and decreased drug effects when cimetidine is co-administered.
• Awareness of potential interactions with other hepatically metabolized drugs is crucial for safe patient management.